By Benjamin Mallet and Sudip Kar-Gupta PARIS (Reuters) -France stepped up security measures on Sunday as farmers prepared to converge on Paris as part of nationwide protests from agricultural workers demanding better pay and living conditions. Farmers in France, the European Union’s biggest agricultural producer, have complained of unfair competition from rivals in more lightly regulated countries. Over the last week, they have set up roadblocks on motorways to highlight their cause. They have also damaged property, including local government offices. Some farmers’ unions called for protesters…